1. Field of the Invention
The present invention relates generally to Global Positioning System (GPS) receivers, and in particular, to a glitchless clock multiplexer controlled by an asynchronous select signal used in GPS receivers.
2. Description of the Related Art
The use of GPS in consumer products has become commonplace. Hand-held devices used for mountaineering, automobile navigation systems, and GPS for use with cellular telephones are just a few examples of consumer products using GPS technology.
As GPS technology is being combined with these devices, the GPS chips are being placed in widely ranging applications. Some of these applications require that the GPS receiver function at low power levels, where GPS receiver manufacturers utilize techniques to shut off portions of the GPS receiver to conserve power consumption.
However, when the power is turned off to portions of the GPS receiver, it requires interesting partitions of the GPS receiver chips, such that those portions that must remain on to provide functionality are powered on for all power modes. One such example is the use of a Voltage Controlled Oscillator (VCO) to provide clock functions to the baseband processor of the GPS receiver. Typically, the VCO is part of the Radio Frequency (RF) portion of the GPS receiver, and must remain powered on during GPS low power modes of operation. This increases overall power draw because at least the VCO must remain powered on during low power modes, or a second VCO must be constructed for use by the baseband processor portion, making design and integration more difficult.
It can be seen, then, that there is a need in the art to reduce power consumption on GPS receivers. It can also be seen that there is a need in the art to be able to provide clocking functions to the baseband processor of a GPS receiver in low power modes of operation.